Updating an AngularJS directive following a service method invocation

Question

Updating an AngularJS directive following a service method invocation

My goal is to set up a reusable alert service that can be easily called from anywhere in my application with just:

alertService.showAlert('warning', 'something went wrong!');

One example of where I want to use this is after an AJAX call to a backend API. Currently, I am using a factory and a directive for this purpose. However, it seems like something is not working correctly because the directive does not update after calling the showAlert method. Here's a simplified version of what I have so far:

var srv = angular.module('srv', []);
srv.factory('alertService', ['$timeout', function($timeout){
    var alertService = this;
        alertService.alertNeeded = false;
        alertService.alertClass = '';
        alertService.alertMessage = '';
        alertService.setAlertNeeded = function(){
            alertService.alertNeeded = true
        };
        alertService.setAlertClass = function(type){
            if(type === 'warning')
                alertService.alertClass = 'alert-warning';
            if(type === 'success')
                alertService.alertClass = 'alert-success';
            if(type === 'info')
                alertService.alertClass = 'alert-info';
            if(type === 'danger')
                alertService.alertClass = 'alert-danger';
        };
        alertService.setAlertMessage = function(message){
            alertService.alertMessage = message;
        };

        return {
            showAlert: function(class, msg){
                alertService.setAlertNeeded();
                alertService.setAlertClass(class);
                alertService.setAlertMessage(msg);
            }
        };
 }]).
directive('myAlerts', ['alertService', function(alertService){
        return {
            restrict: 'A',
            template: '<div ng-class="alertClass" ng-show="alertNeeded">{{alertMessage}}</div>',
            link: function(scope){                   
                    scope.alertNeeded = alertService.alertNeeded;
                    scope.alertMessage = alertService.alertMessage;
                    scope.alertClass = alertService.alertClass;
            }
        }
    }]).
controller('alertShowingController', ['$scope', 'alertService', function($scope, alertService){
     alertService.showAlert('warning', 'Warning alert!!!')   
 }]);

Although my code is slightly different, the concept remains the same - I want to trigger alertService.showAlert(...) from another controller in a different module (which depends on the srv module) to update the variables in the myAlerts directive and display the correct alert.

The issue I'm facing is that after calling the showAlert method, the values are set properly, but within the directive code, I'm receiving alertService.alertNeeded as undefined.

I am new to AngularJS, so there might be something fundamental that I am missing. I've spent a lot of time trying to figure it out, but I haven't found a solution yet.

Please provide some guidance!

javascript angularjs angularjs-directive

Answer 1

Answer №1

Here's a pattern I've utilized in the past:

var srv = angular.module('srv', []);
srv.factory('alertService', ['$timeout', function($timeout){
    var alertListeners = [];

    this.register = function (listener) {
        alertListeners.push(listener);
    };

    this.notifyAll = function (data) {
        for (// each listener in array) {
            var listenerObject = alertListeners[i];
            try { // do not allow exceptions in individual listeners to corrupt other listener processing
                listenerObject.notify(data);
            } catch(e) {
                    console.log(e);
            }   
        }
    };
 }]).
 directive('myAlerts', ['alertService', function(alertService){

     var alertDirectiveObserver = function($scope, alertService) {

         this.notify = function(data) {
            /*
             * TO DO - utilize data to display alert
             */
         };

         alertService.register(this);
     };


   return {
     restrict: 'A',
     template: '<div ng-class="alertClass" ng-show="alertNeeded">{{alertMessage}}</div>',
     controller: ['$scope', 'alertService', alertDirectiveObserver],
     link: function(scope){  
     }
    }
}]).
controller('alertShowingController', ['$scope', 'alertService',   function($scope, alertService){
    alertService.notifyAll({'warning', 'Warning alert!!!'})   
 ]);

Remember to also clean up by registering a function to remove objects on scope destroy.

For example:

element.on('$destroy', function() {
    alertService.unregister(// some listener id);
});

Answer 2

Here's a pattern I've utilized in the past:

var srv = angular.module('srv', []);
srv.factory('alertService', ['$timeout', function($timeout){
    var alertListeners = [];

    this.register = function (listener) {
        alertListeners.push(listener);
    };

    this.notifyAll = function (data) {
        for (// each listener in array) {
            var listenerObject = alertListeners[i];
            try { // do not allow exceptions in individual listeners to corrupt other listener processing
                listenerObject.notify(data);
            } catch(e) {
                    console.log(e);
            }   
        }
    };
 }]).
 directive('myAlerts', ['alertService', function(alertService){

     var alertDirectiveObserver = function($scope, alertService) {

         this.notify = function(data) {
            /*
             * TO DO - utilize data to display alert
             */
         };

         alertService.register(this);
     };


   return {
     restrict: 'A',
     template: '<div ng-class="alertClass" ng-show="alertNeeded">{{alertMessage}}</div>',
     controller: ['$scope', 'alertService', alertDirectiveObserver],
     link: function(scope){  
     }
    }
}]).
controller('alertShowingController', ['$scope', 'alertService',   function($scope, alertService){
    alertService.notifyAll({'warning', 'Warning alert!!!'})   
 ]);

Remember to also clean up by registering a function to remove objects on scope destroy.

For example:

element.on('$destroy', function() {
    alertService.unregister(// some listener id);
});

Answer 3

Answer №2

Your code has a mix-up with the alertService variable, as it has different meanings within the factory definition and outside of it. To resolve this issue, you can add some missing methods to the object returned by the factory:

return {
    showAlert: function(cssClass, msg){
        alertService.setAlertNeeded();
        alertService.setAlertClass(cssClass);
        alertService.setAlertMessage(msg);
    },

    alertClass: function() { return alertService.alertClass; },     
    alertMessage: function() { return alertService.alertMessage; },
    alertNeeded: function() { return alertService.alertNeeded; }
};

After updating the object's methods, you will need to adjust your directive's template to utilize these functions on each digest cycle:

directive('myAlerts', ['alertService', function(alertService){
        return {
            restrict: 'A',
            template: '<div ng-class="alertClass()"' +
                      '     ng-show="alertNeeded()">' +
                      '  {{alertMessage()}}' +
                      '</div>',
            link: function(scope){                   
                scope.alertNeeded = alertService.alertNeeded;
                scope.alertMessage = alertService.alertMessage;
                scope.alertClass = alertService.alertClass;
            }
        }
}])

By making these adjustments, you should be able to display your warning message correctly. Give it a try in a fiddle.

Answer 4

Your code has a mix-up with the alertService variable, as it has different meanings within the factory definition and outside of it. To resolve this issue, you can add some missing methods to the object returned by the factory:

return {
    showAlert: function(cssClass, msg){
        alertService.setAlertNeeded();
        alertService.setAlertClass(cssClass);
        alertService.setAlertMessage(msg);
    },

    alertClass: function() { return alertService.alertClass; },     
    alertMessage: function() { return alertService.alertMessage; },
    alertNeeded: function() { return alertService.alertNeeded; }
};

After updating the object's methods, you will need to adjust your directive's template to utilize these functions on each digest cycle:

directive('myAlerts', ['alertService', function(alertService){
        return {
            restrict: 'A',
            template: '<div ng-class="alertClass()"' +
                      '     ng-show="alertNeeded()">' +
                      '  {{alertMessage()}}' +
                      '</div>',
            link: function(scope){                   
                scope.alertNeeded = alertService.alertNeeded;
                scope.alertMessage = alertService.alertMessage;
                scope.alertClass = alertService.alertClass;
            }
        }
}])

By making these adjustments, you should be able to display your warning message correctly. Give it a try in a fiddle.

Updating an AngularJS directive following a service method invocation

Answer №1

Answer №2

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